The present invention provides an improved railway truck friction shoe. More particularly, a friction shoe is provided which has improved vertical stability and extended wear life.
The type of railway car truck to which the present invention relates comprises, generally, spaced side frames, each of which has an opening arranged to support opposite ends of a bolster. Spring biased friction shoes are provided, having walls engageable with friction surfaces in the side frame opening. Two friction shoes engage each end of the side frame and bolster for controlling the oscillating movement of the bolster.
Typically, there are two major concerns in the design of railway truck friction shoes. One is that the stability of the friction shoe be maintained in order that excessive forces not be transmitted to the bolster or the side frame by the tilting and subsequent jamming of the shoe during its operation. Another is to extend the wear life of the friction shoe by evenly distributing the contact pressures across the side frame column face of the shoe.
U.S. Pat. No. 4,109,585, assigned to the assignee of the present invention, discloses an improved friction shoe wherein the friction shoe has extended wing surfaces that are inclined with respect to the guiding surfaces of the bolster. The present invention is concerned with further improvements and modifications to the friction shoe of this patent, and also to a friction shoe having a solid slope surface without wings.
It is an object of the present invention to provide an improved railway truck friction shoe with improved vertical stability and extended wear life.
The present invention provides an improved railway truck friction shoe wherein the contact point of the shoe with the bolster is substantially coincident with the bias spring center line, and, further, is substantially equidistant between the top and bottom edges of the column face of the shoe. The bias spring is located within the shoe as close to the side frame column as allowed by the required spring radius and wall thickness of the shoe. In an alternative embodiment, the spring engages a solid lower surface of the friction shoe which has a solid slope surface without wings. Further, the crown radius of the slope surface of the shoe or the wings of the shoe is reduced from the prior art known radii. Further, the length of the vertical or side frame column face of the shoe is increased. The combination of these features leads to an improved friction shoe exhibiting the features of improved vertical stability and extended wear life.